BOMBYLIIDAE ACROCERIDAE 



489 



spretus are emptied of their contents by the larvae of Systoechus 



oreas and Triodites mus. A similar observation has been made 



in the Troad by Mr. Calvert, who found tliat the Bombyliid, 



Canostoynafascijyennis, destroys large cjuantities of the eggs of 



Caloptenus italicus. Still more recently ]\I. Kiinckel d'Herculais 



has discovered that the destructive 



locust StauTonohis marocccums is 



kept in check in Algeria in a 



similar manner, as many as 80 



per cent of the eggs of the locust 



being thus destroyed in certain 



localities. He observes that the 



larva of the fly, after being full 



fed in the autumn, passes the 



winter in a state of lethargy — 



he calls it " hypnody " — in the 



Fig. 233. — Si/Mro2}us c-naldis. South 

 Africa. A, Vwpa, ; B, imago, ap- 

 pendages of the left side removed. 

 (After Westwood.) 



egg-case of the locust, and he 

 further informs us that in the 

 case oi Anthrax fetiestral is, wliich 

 devours the eggs of the large 

 Ocnerodes, the lethargy may be prolonged for a period of three 

 years. After the pupa is formed it works a way out of the case 

 by means of its armature, and then again becomes for some days 

 immobile before the perfect fly appears. Lepidopterous larvae 

 are also attacked by Bombyliid flies. A species of Systropus has 

 been recorded as destroying the larva of Limacodes. Several of 

 the Bombyliids of the genus just mentioned are remarkable for 

 the great resemblance they display to various Hymenoptera, some 

 of them being very slender flies, like the thin bodied fossorial 

 Hymenoptera. The difference between the pupa and imago in 

 this case is very remarkalile (Fig. 2 00). 



Fam. 21. Acroceridae or Cyrtidae. — Flies of the average size, 

 of peculiar form, the small head consisting cdmost entirely of the 

 eyes, and hent down tinder the humped thorax : ivings smcdl, halteres 

 entirely concecded hy the very la.rge horizontal squamae; antennae 

 very diverse. The peculiar shape of these flies is an exaggeration of 

 that we have already noticed in Bonibylius. The mouth in Acro- 

 ceridae is very variable ; there may be a very long, slender proboscis 

 {Acrocera), or the mouth-parts may be so atrophied that it is 

 doubtful whether even an orifice exists (Ogcodes). There are but 



